&nbsp436 &nbspFXUS61 KPHI 141945 &nbspAFDPHI &nbsp &nbspAREA FORECAST DISCUSSION &nbspNATIONAL WEATHER SERVICE MOUNT HOLLY NJ &nbsp345 PM EDT TUE AUG 14 2018 &nbsp&nbsp &nbspSYNOPSIS &nbsp &nbspTHE LARGE LOW PRESSURE SYSTEM THAT HAS BEEN RESPONSIBLE FOR THE &nbspHEAVY RAIN IN THE AREA THE LAST FEW DAYS WILL CONTINUE TO SLOWLY &nbspLIFT NORTHEAST OVERNIGHT AWAY FROM THE REGION. THIS WILL BE FOLLOWED &nbspBY WEAK HIGH PRESSURE TOMORROW. BY FRIDAY, ANOTHER LOW CROSSING FROM &nbspTHE GREAT LAKES REGION INTO NEW ENGLAND WILL BRING A COLD FRONT INTO &nbspOUR REGION. THIS FRONT IS EXPECTED TO STALL OVER OUR REGION FOR MUCH &nbspOF THE WEEKEND BEFORE SHIFTING SOUTHEAST SUNDAY NIGHT OR MONDAY. &nbsp &nbsp &nbsp&nbsp &nbspNEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/ &nbsp &nbspA CLEAR SPIN IN THE ATMOSPHERE WAS EVIDENT THIS AFTERNOON ON &nbspREGIONAL MOSAIC RADAR AND GOES-16 SATELLITE LOOPS IN ASSOCIATION &nbspWITH A CLOSED UPPER LOW OVER THE CATSKILLS REGION IN UPSTATE NY. &nbspTHIS PLACES OUR REGION UNDER THE DRY SLOT AND IN WESTERLY FLOW TO &nbspTHE SOUTH OF THE CYCLONE. HOWEVER, THIS DRY SLOT IS NOT VERY DRY AS &nbspTHE PLUME OF TROPICAL MOISTURE THAT WAS DRAWN POLEWARD AHEAD OF THIS &nbspSYSTEM HAS WRAPPED AROUND THE LOW, RESULTING IN PWATS THAT ARE NEAR &nbspOR SLIGHTLY ABOVE CLIMO (1.5-1.75"). &nbsp &nbspSUFFICIENT MOISTURE AND DIURNAL INSTABILITY COMBINED WITH SEVERAL &nbspSOURCES OF LIFT, HAS LEAD TO ANOTHER EPISODE OF SHOWERS AND STORMS &nbspTHIS AFTERNOON. CONVECTION WAS LOOSELY ORGANIZED EARLIER THIS &nbspAFTERNOON BUT HAS SINCE ORGANIZED A BIT INTO AT LEAST THREE BROKEN &nbspLINE SEGMENTS: (1) ALONG A PRE-FRONTAL SURFACE TROUGH THAT WAS OVER &nbspTHE I-95 CORRIDOR AT THE MOMENT AND (2)/(3) A TRAILING SHORTWAVE &nbspTROUGHS LOCATED OVER NORTH-CENTRAL AND EASTERN PA. THIS MEANS &nbspSEVERAL ROUNDS OF SHOWERS AND STORMS WILL AFFECT EASTERN PA AND NJ &nbspTHROUGH THE REMAINDER OF THE AFTERNOON AND INTO THE EVENING. THE &nbspBULK OF THIS ACTIVITY THIS AFTERNOON MAY PASS TO THE NORTH OF &nbspDELMARVA BUT THE TRAILING CONVECTION COULD ADVANCE FARTHER SOUTH &nbspINTO THESE SOUTHERN ZONES THIS EVENING. &nbsp &nbspHEAVY DOWNPOURS WITH THESE SHOWERS AND STORMS ARE PRODUCING A QUICK &nbspONE- TO THREE-QUARTERS OF AN INCH BUT A STEADY STORM MOTION (EAST AT &nbsp10-20 MPH) HAS LIMITED THE DURATION OF THE HEAVY RAIN AND THE THREAT &nbspOF FLASH FLOODING. NONETHELESS, POOR DRAINAGE FLOODING IS STILL A &nbspPOSSIBILITY FOR LOCATIONS THAT SEE MULTIPLE ROUNDS OF BRIEF HEAVY &nbspDOWNPOURS AND ARE PARTICULAR FLOOD PRONE DUE TO THE RECENT HEAVY &nbspRAINFALL. UNDER THE ASSUMPTION THAT STORMS DON'T ORGANIZE ALONG A &nbspMORE WEST-EAST LINE (PARALLEL TO STORM MOTION AND FAVORABLE TO &nbspTRAINING), THE RISK FOR FLASH FLOODING WILL BE LOW. &nbsp &nbspSHOWERS AND STORMS WILL DIMINISH IN COVERAGE AND INTENSITY AFTER &nbspSUNSET, BUT AN ISOLATED SHOWER IS STILL POSSIBLE EARLY INTO THE &nbspOVERNIGHT. A LIGHT WEST WIND AND CLOUD COVER SHOULD LIMIT THE &nbspDEVELOPMENT OF FOG (IN TERMS OF COVERAGE AND DENSITY). HOWEVER, &nbspPATCHY FOG CANNOT BE RULED OUT IN THE RURAL VALLEYS IF CLOUD BREAKS &nbspDO DEVELOP. &nbsp &nbsp &nbsp&nbsp &nbspSHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/ &nbsp &nbspTHE UPPER TROUGH WILL MOVE OFF THE NEW ENGLAND COAST WHILE THE &nbspATTENDANT COLD FRONT PROGRESSES FARTHER OFF THE MID-ATLANTIC COAST. &nbspAN UPPER SHORTWAVE RIDGE INITIALLY POSITIONED WEST OF THE &nbspAPPALACHIAN SPINE IN THE MORNING WILL BUILD EASTWARD TOWARD THE AREA &nbspTHROUGH THE DAY. &nbsp &nbspTHE AFORMENTIONED RIDGE MAY BE FAR ENOUGH UPSTREAM OF OUR AREA TO &nbspGUARANTEE ONE OF THOSE FLEETING DAYS WITHOUT ANY SHOWERS OR STORMS. &nbspTHE POSSIBILITY FOR A WEAK SHORTWAVE DISTURBANCE RIDING ATOP OF THE &nbspRIDGE, DEVELOPMENT OF A PRESSURE TROUGH AND TERRAIN CIRCULATIONS &nbspCOULD PROVIDE A SOURCE(S) OF LIFT FOR CONVECTIVE INITIATION DURING &nbspPEAK HEATING HOURS, MAINLY ACROSS THE HIGHER TERRAIN AND NORTHERN &nbspTIER OF THE CWA (I-78 NORTH). COVERAGE (POPS) ARE FORECAST TO BE &nbspHIGHEST LATE IN THE AFTERNOON BUT LIMITED TO LOW CHANCE (30 PERCENT) &nbspACROSS THE SOUTHERN POCONOS AND ISOLATED (20 PERCENT) ELSEWHERE N/W &nbspOF THE FALL LINE AND MASON-DIXON LINE. &nbsp &nbspWAA IN WAKE OF THE EXITING TROUGH IN ADDITION TO STRONG DAYTIME &nbspHEATING AND DOWNSLOPING FLOW WILL ALL CONTRIBUTE TO A WARMING TREND &nbspCOMPARED TO RECENT DAYS. HIGHS IN THE LOWER 90S ARE FORECAST FOR THE &nbspURBAN I-95 CORRIDOR AND COASTAL PLAIN WITH UPPER 80S MORE COMMON &nbspFARTHER INLAND IN THE HIGHER TERRAIN. &nbsp &nbsp &nbsp&nbsp &nbspLONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/ &nbsp &nbspSUMMARY...RELATIVE CALM WEDNESDAY NIGHT AND THURSDAY WILL BE SHORT &nbspLIVED AS ANOTHER LOW PRESSURE SYSTEM WILL BRING MORE CHANCES FOR &nbspRAIN FRIDAY THROUGH THE WEEKEND. WE MAY HAVE ANOTHER PERIOD OF &nbspTRANQUIL WEATHER ON MONDAY, BEFORE A STRONGER COLD FRONT COULD BRING &nbspANOTHER ROUND OF STORMS TUESDAY OR LATER. &nbsp &nbspDETAILS: &nbsp &nbspWEDNESDAY NIGHT AND THURSDAY...A MID LEVEL RIDGE IS EXPECTED TO &nbspPROGRESS EAST THROUGH THIS PERIOD, ALTHOUGH IT WILL BE WEAKENING AS &nbspIT DOES SO. THEREFORE, THE PERIOD SHOULD BE STARTING OUT MOSTLY DRY, &nbspTHOUGH SOME SHOWERS AND STORMS COULD ENCROACH ON REGION FROM THE WEST &nbspON THURSDAY AS THE NEXT LOW BEGINS TO DEVELOP. WITH THURSDAY &nbspSTARTING OFF MOSTLY SUNNY, AND DEW POINTS EXPECTED TO REMAIN IN THE &nbspLOWER 70S, WE WILL SEE HOT AND MUGGY CONDITIONS DURING THE DAY &nbspTHURSDAY. CURRENT FORECAST HAS CONDITIONS BELOW HEAT ADVISORY &nbspCRITERIA, BUT WILL CONTINUE TO MONITOR THIS AS WE GET CLOSER. &nbsp &nbspFRIDAY THROUGH SUNDAY...DEVELOPING LOW OVER THE GREAT LAKES REGION &nbspWILL PROGRESS TOWARDS NEW ENGLAND THROUGH THE WEEKEND. THIS LOW WILL &nbspBRING A COLD FRONT INTO OUR REGION ON FRIDAY. HOWEVER, IT STILL &nbspLOOKS LIKELY THAT THIS FRONT WILL STALL OVER OUR REGION FOR MUCH OF &nbspTHE REST OF THE WEEKEND. CONSEQUENTLY, EXPECT CONTINUED CHANCES FOR &nbspSHOWERS AND STORMS THROUGH THE WEEKEND, ESPECIALLY ON FRIDAY AND &nbspFRIDAY NIGHT. HOWEVER, THANKFULLY, IT LOOKS LIKE WE SHOULD HAVE &nbspFASTER STORM MOTIONS LIMITING THE FLOODING THREAT, ALTHOUGH &nbspPRECIPITABLE WATER VALUES REMAIN QUITE HIGH. TEMPERATURES THROUGH &nbspTHIS PERIOD WILL BE VERY DEPENDENT ON WHERE THE FRONT EVENTUALLY &nbspSTALLS. ESPECIALLY ON FRIDAY, WE COULD SEE A LARGE TEMPERATURE &nbspGRADIENT ACROSS OUR REGION WITH THE COASTAL PLAINS ONCE AGAIN IN THE &nbspLOWER 90S (HEAT INDEX VALUES NEAR 100), WHILE THE SOUTHERN POCONOS &nbspMAY STRUGGLE TO REACH 80. &nbsp &nbspMONDAY...MID AND UPPER LEVEL SHORT WAVE RIDGE IS EXPECTED TO QUICKLY &nbspPROPAGATE EAST OVER OUR REGION RESULTING IN A MOSTLY DRY DAY. &nbsp &nbspTUESDAY AND BEYOND...THIS WILL BE A PERIOD WORTH WATCHING AS ALMOST &nbspALL OF THE OPERATIONAL MODELS ARE DEPICTING A STRONGER COLD FRONT &nbspAPPROACHING OUR REGION FROM THE WEST. THERE REMAIN SOME MAJOR TIMING &nbspDIFFERENCES (THE GFS DOESN'T DEPICT THIS FRONT COMING THROUGH AT ALL &nbspTHROUGH THE FIRST HALF OF THE WEEK, WHILE THE ECMWF HAS IT THROUGH &nbspTHE REGION TUESDAY NIGHT), BUT IF THIS PATTERN CONTINUES, THIS COULD &nbspFINALLY BRING IN MUCH DRIER AIR (AFTER A PERIOD OF SHOWERS AND &nbspSTORMS ALONG AND JUST AHEAD OF THE FRONT). &nbsp &nbsp &nbsp&nbsp &nbspAVIATION /20Z TUESDAY THROUGH SUNDAY/ &nbsp &nbspTHE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, &nbspKMIV, KACY AND SURROUNDING AREAS. &nbsp &nbspTHROUGH THIS EVENING...SEVERAL BROKEN LINES OF SHOWERS AND STORMS &nbspWILL MOVE EASTWARD THROUGH THE REGION. THIS ACTIVITY DOES NOT LOOK &nbspTO AFFECT A TERMINAL FOR MORE THAN 15-20 MINUTES, RESULTING IN ONLY &nbspBRIEF MVFR OR IFR RESTRICTIONS. TIMING EACH ROUND HAS BEEN RATHER &nbspCHALLENGING WITH NEAR TERM TAF AMENDMENTS BASED ON UPSTREAM RADAR &nbspTRENDS SEEMS TO BE THE MOST PRACTICAL APPROACH. THIS ACTIVITY SHOULD &nbspDIMINISH LATE THIS EVENING. &nbsp &nbspOVERNIGHT...A BROKEN MID-LEVEL DECK AND W-NW FLOW 4-8 KT SHOULD &nbspLIMIT THE POTENTIAL FOR FOG DEVELOPMENT. THE CURRENT FORECAST IS FOR &nbspVFR OVERNIGHT. &nbsp &nbspWEDNESDAY...PREDOMINATELY VFR. AN ISOLATED SHOWER OR STORM IS &nbspPOSSIBLE, MAINLY IN WESTERN TERMINALS (ABE/RDG) AND LATE IN THE &nbspAFTERNOON. ANY RESTRICTIONS WOULD BE BRIEF AND LOCALIZED. W WIND 5- &nbsp10 KT WITH GUSTS OF 15-20 KT EXPECTED. &nbsp &nbspOUTLOOK... &nbsp &nbspWEDNESDAY NIGHT...VFR CONDITIONS EXPECTED WITH LIGHT WESTERLY WINDS. &nbspPATCHY FOG MAY DEVELOP NEAR MORE RURAL TAF SITES, BUT CHANCE FOR &nbspTHIS OCCURING IS LOW. HIGH CONFIDENCE ON THE REST OF THE FORECAST &nbspELEMENTS. &nbsp &nbspTHURSDAY THROUGH SUNDAY...PREDOMINANTLY VFR WITH TEMPORARY &nbspVISIBILITY AND CEILING RESTRICTIONS IF ANY SHOWERS AND THUNDERSTORMS &nbspAFFECT A TAF SITE. THE HIGHEST RISK FOR THIS OCCURING IS ON FRIDAY &nbspAND FRIDAY NIGHT. SOUTHWESTERLY WIND WILL BE SHIFTING TO NORTHERLY &nbspAND EVENTUALLY NORTHEASTERLY SATURDAY NIGHT INTO SUNDAY AS A COLD &nbspFRONT SINKS SOUTH. &nbsp &nbsp &nbsp&nbsp &nbspMARINE &nbsp &nbspW-SW WINDS 10-15 KT WITH GUSTS TO 20 KT ARE OCCURRING THIS AFTERNOON &nbspIN THE DE BAY AND COASTAL ATLANTIC WATERS. MEANWHILE SEAS AROUND &nbspAROUND 4 FT IN THE COASTAL WATERS. EXPECT THESE CONDITIONS TO &nbspCONTINUE INTO THIS EVENING EXCEPT FOR A WIND SHIFT TO W OR EVEN W-NW &nbspWILL OCCUR BEHIND A FRONT AROUND OR SHORTLY AFTER SUNSET. A PRESSURE &nbspSURGE BEHIND THE FRONT COULD ALSO YIELD GUSTS NEAR 25 KT (SCA &nbspCRITERIA) BUT IT SHOULD ONLY LAST FOR AN HOUR OR TWO PER MODEL &nbspFORECAST SOUNDINGS. ACCORDINGLY A SCA WAS NOT ISSUED. ISOLATED TO &nbspSCATTERED STORMS OVER LAND SHOULD REACH THE NJ WATERS LATE THIS &nbspAFTERNOON. ISOLATED GUSTS AT OR ABOVE 30 KT ARE POSSIBLE AND COULD &nbspNECESSITATE SPECIAL MARINE WARNINGS. ANOTHER BROKEN LINE OF STORMS &nbspEVEN FARTHER INLAND MAY REACH THE WATERS CLOSER TO SUNSET BUT IT IS &nbspUNCERTAIN IF THE INTENSITY WILL HOLD TOGETHER BY THE TIME IT REACHES &nbspTHE COASTAL WATERS. &nbsp &nbspW WINDS 10-15 WITH GUSTS TO 20 KT ARE EXPECTED ON WEDNESDAY. &nbsp &nbspOUTLOOK... &nbsp &nbspTHURSDAY...WINDS AND SEAS SHOULD STAY BELOW SCA CRITERIA. &nbsp &nbspFRIDAY...SOUTHERLY WINDS ON THE ATLANTIC WATERS WILL BE INCREASING &nbspAND COULD GUST ABOVE 20 KT AT TIMES. SEAS WILL SUBSEQUENTLY INCREASE &nbspAS WELL. HOWEVER, AT THIS TIME IT LOOKS LIKELY THAT BOTH WINDS AND &nbspSEAS WILL STAY JUST BELOW SCA CRITERIA. &nbsp &nbspSATURDAY AND SUNDAY...WINDS WILL GRADUALLY SHIFT TO WESTERLY AND &nbspTHEN ABRUPTLY SHIFT TO NORTHERLY AND NORTHEASTERLY SATURDAY NIGHT &nbspINTO SUNDAY. BEHIND THIS COLD FRONT, WIND GUSTS TO 25 KT AND SEAS &nbspAPPROACHING 5 FEET ARE POSSIBLE. &nbsp &nbspRIP CURRENTS... &nbsp &nbspA LOW RISK FOR THE DEVELOPMENT OF DANGEROUS RIP CURRENTS IS EXPECTED &nbspFOR THE REMAINDER OF THIS AFTERNOON AND WEDNESDAY AS THE FLOW &nbspREMAINS OFFSHORE. &nbsp &nbsp &nbsp&nbsp &nbspPHI WATCHES/WARNINGS/ADVISORIES &nbsp &nbspPA...NONE. &nbspNJ...NONE. &nbspDE...NONE. &nbspMD...NONE. &nbspMARINE...NONE. &nbsp &nbsp &nbsp &nbsp &nbspSYNOPSIS...JOHNSON &nbspNEAR TERM...KLEIN &nbspSHORT TERM...KLEIN &nbspLONG TERM...JOHNSON &nbspAVIATION...JOHNSON/KLEIN &nbspMARINE...JOHNSON/KLEIN &nbsp